{"id":"CVE-2026-80978","summary":"net: cap advertised IP tunnel headroom","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: cap advertised IP tunnel headroom\n\nIP tunnel devices derive their advertised needed_headroom from lower\noutput devices. A stack of user-created devices can make the derived\nvalue larger than the 16-bit skb header offsets can represent. Once IP\noutput reserves it, skb head expansion can wrap those offsets.\n\nThe runtime transmit path already caps a growing needed_headroom at 512.\nApply the same cap when tunnel configuration publishes needed_headroom\nderived from a lower output device.\n\nCapping the advertised value is safe: IP tunnel transmit still expands\nthe skb when a packet needs more headroom. A nonsensical stacked\nconfiguration can therefore incur an extra reallocation, but it cannot\npublish an unbounded reservation to upper layers.","modified":"2026-09-14T03:45:56.154191220Z","published":"2026-09-11T19:42:39.496Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80978.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/6b222adeb9340306e2ff97127c76117abb9b3df8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9144f2c53a04465a6878172b523f640313c5559e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/af0ee8f04bea22cdb331fa3509e17f81b48938ad"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bc4e05ae66c9797a0972ac44326e69c5305e0020"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80978.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80978"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"1a37e412a0225fcba5587f24c0dfc7636efc8b69"},{"fixed":"bc4e05ae66c9797a0972ac44326e69c5305e0020"},{"fixed":"af0ee8f04bea22cdb331fa3509e17f81b48938ad"},{"fixed":"9144f2c53a04465a6878172b523f640313c5559e"},{"fixed":"6b222adeb9340306e2ff97127c76117abb9b3df8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80978.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.11.0"},{"fixed":"6.12.109"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.50"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80978.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}